This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-269762, filed Sep. 24, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to an electrolyte composition, a photosensitized solar cell using said electrolyte composition, and a method of manufacturing a photosensitized solar cell using said electrolyte composition.
The general structure of a photosensitized solar cell is described in, for example, Japanese Patent Disclosure (Kokai) No. 1-220380. It is described that the solar cell comprises an electrode (oxide electrode) consisting of a transparent semiconductor layer consisting of fine particles of a metal oxide and supporting a dye on the surface, a transparent electrode arranged to face the oxide electrode, and a liquid carrier movement layer-interposed between these two electrodes. Since the carrier movement layer is liquid, the solar cell of this type is called a wet type photosensitized solar cell.
The photosensitized solar cell is operated as follows. Specifically, the light incident on the transparent electrode runs to reach the dye supported on the surface of the transparent semiconductor layer so as to excite the dye. The excited dye promptly delivers electrons to the transparent semiconductor tug layer. On the other hand, the dye charged positive by the loss of electrons receives electrons from the ions diffused from the carrier movement layer so as to be neutralized electrically. The ions that have delivered the electrons are diffused into the transparent electrode so as to receive electrons. The oxide electrode and the transparent electrode positioned to face the oxide electrode act as a negative electrode and a positive electrode, respectively, so as to permit the wet type photosensitized solar cell to be operated.
In the wet type photosensitized solar cell, it is necessary to use a solvent having a low molecular weight and to apply shielding strictly so as to prevent the liquid leakage. However, it is difficult to maintain the shielded state for many years. It is worried about that, by the liquid leakage and evaporation of the solvent molecules, the function of the element may be deteriorated and an air pollution or water contamination may be brought about. Such being the situation, it is proposed to use an ionic conduction type solid electrolyte, which does not contain a solvent of a low molecular weight, or an electron conduction type solid organic material, which does not contain a solvent of a low molecular weight, in place of the liquid carrier movement layer. The solar cell of this type is called a full-solid-state photosensitized solar cell.
The solid-state photosensitized solar cell is certainly free from the problem of the liquid leakage. However, new problems are brought about. Specifically, the electrical resistance is increased. In addition, the solid electrolyte fails to enter sufficiently the clearances among TiO2 particles having a large specific surface area, thereby the contact between the TiO2 particles and the electrolyte is rendered insufficient. As a result, the energy conversion efficiency is lowered. Also, since the semiconductor electrode and the solid conductive material differ from each other in the thermal expansion coefficient, the bonding interface between the semiconductor electrode and the solid conductive material tends to peel off in the course of the beat cycle, leading to deterioration in the energy conversion efficiency.
As described above, the wet type photosensitized solar cell is defective in that leakage tends to be generated in the liquid carrier movement layer and that the solvent to be evaporated. On the other hand, the full-solid-state photosensitized solar cell is defective in that the electrical resistance is increased, that contact between the TiO2 particles and the electrolyte is insufficient, and that the bonding interface between the semiconductor electrode and the solid conductive material tends to be peeled because of the heat cycle.
Under the circumstances, proposed is a photosensitized solar cell provided with a gel electrolyte. The gel electrolyte contains an electrolyte consisting of iodine and an iodide, an organic solvent for dissolving the electrolyte, and a gelling agent. In other words, a solvent for dissolving iodine consists of the organic solvent.
However, the organic solvent tends to be dissipated to the outside through the sealing portion of the solar cell. It follows that the photosensitized solar cell comprising the gel electrolyte of the composition described above gives rise to the problem that the composition of the gel electrolyte is changed by the evaporation of the organic solvent, leading to a low energy conversion efficiency.
The present invention is intended to provide an electrolyte composition capable of improving the energy conversion efficiency of a solar cell and also capable of obtaining a high energy conversion efficiency when the solar cell is used under an environment of a high temperature, a photosensitized solar cell comprising the particular electrolyte composition, and a method of manufacturing the particular photosensitized solar cell.
According to a first aspect of the present invention, there is provided an electrolyte composition, comprising:
an electrolyte containing at least one kind of an imidazolium salt selected from the group consisting of 1-methyl-3-propyl imidazolium iodide, 1-methyl-3-isopropyl imidazolium iodide, 1-methyl-3-butyl imidazolium iodide, 1-methyl-3-isobutyl imidazolium iodide and 1-methyl-3-sec-butyl imidazolium iodide;
a halogen-containing compound dissolved in the electrolyte; and
a compound dissolved in the electrolyte and containing at least one element selected from the group consisting of N, P and S. the compound being capable of forming an onium salt together with the halogen-containing compound.
According to a second aspect of the present invention, there is provided a photosensitized solar cell, comprising an n-type semiconductor electrode having a surface on which a dye is adsorbed; a counter substrate arranged to face the n-type semiconductor electrode; a conductive film formed on that surface of the counter substrate which faces the n-type semiconductor electrode; and a gel electrolyte serving to relay the charge transfer between the conductive film and the n-type semiconductor electrode, the gel electrolyte containing a polymer of an onium salt formed between a halogen-containing compound and a compound containing at least one element selected from the group consisting of N, P and S, and an electrolyte containing at least one kind of an imidazolium salt selected from the group consisting of 1-methyl-3-propyl imidazolium iodide, 1-methyl-3-isopropyl imidazolium iodide, 1-methyl-3-butyl imidazolium iodide, 1-methyl-3-isobutyl imidazolium iodide, and 1-methyl-3-sec-butyl imidazolium iodide.
Further, according to a third aspect of the present invention, there is provided a method of manufacturing a photosensitized solar cell comprising an n-type semiconductor electrode having a surface on which a dye is adsorbed, a counter substrate arranged to face the n-type semiconductor electrode, a conductive film formed on that surface of the counter substrate which faces the n-type semiconductor electrode, and a gel electrolyte serving to relay the charge transfer between the conductive film and the n-type semiconductor electrode, the method comprising the steps of:
allowing an electrolyte composition to be injected into a gap between the n-type semiconductor electrode and the conductive film and to permeate the n-type semiconductor electrode, and the electrolyte composition which comprises an electrolyte containing at least one kind of an imidazolium salt selected from the group consisting of 1-methyl-3-propyl imidazolium iodide, 1-methyl-3-isopropyl imidazolium iodide, 1-methyl-3-butyl imidazolium iodide, 1-methyl-3-isobutyl imidazolium iodide and 1-methyl-3-sec-butyl imidazolium iodide, a halogen-containing compound dissolved in the electrolyte and a compound dissolved in the electrolyte and containing at least one element selected from the group consisting of N, P and S, and the compound being capable of forming an onium salt together with the halogen-containing compound; and
forming a polymer of an onium salt between the compound containing the at least one element and the halogen-containing compound so as to allow the electrolyte composition to gel, thereby obtaining a gel electrolyte.
According to an aspect of the present invention, there is provided an electrolyte composition, comprising:
an electrolyte containing a reversible redox couple;
a halogen-containing compound dissolved in the electrolyte; and
a compound dissolved in the electrolyte, capable of forming an onium salt together with the halogen-containing compound, and having at least one kind of a nitrogen-containing atomic group selected from the group consisting of primary amino group, secondary amino group and tertiary amino group.
According to another aspect of the present invention, there is provided a photosensitized solar cell, comprising:
an n-type semiconductor electrode having a surface on which a dye is adsorbed;
a counter substrate arranged to face the n-type semiconductor electrode;
a conductive film formed on that surface of the counter substrate which faces the n-type semiconductor electrode; and
a gel electrolyte serving to relay the charge transfer between the conductive film and the n-type semiconductor electrode, and gel electrolyte containing a polymer of an onium salt formed between a halogen-containing compound and a compound having at least one kind of a nitrogen-containing atomic group selected from the group consisting of primary amino group, secondary amino group and tertiary amino group, and an electrolyte containing a reversible redox couple.
Further, according to still another aspect of the present invention, there is provided a method of manufacturing a photosensitized solar cell comprising an n-type semiconductor electrode having a surface on which a dye is adsorbed, a counter substrate arranged to face the n-type semiconductor electrode, a conductive film formed on that surface of the counter substrate which faces the n-type semiconductor electrode, and a gel electrode serving to relay the charge transfer between the conductive film and the n-type semiconductor electrode, the method comprising the steps of:
allowing an electrolyte composition to be injected into a gap between the n-type semiconductor electrode and the conductive film and to permeate the n-type semiconductor electrode, the electrolyte composition containing an electrolyte containing a reversible redox couple, a halogen-containing compound dissolved in the electrolyte, and a compound dissolved in the electrolyte and capable of forming an onium salt together with the halogen-containing compound, and the compound having at least one kind of a nitrogen-containing atomic group selected from the group consisting of primary amino group, secondary amino group and tertiary amino group; and
forming a polymer of an onium salt between the compound having the at least one kind of the nitrogen-containing atomic group and the halogen-containing compound so as to allow the electrolyte composition to gel, thereby obtaining a gel electrolyte.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.